Tensioning device



June 24, 1930, I I KERR- 1,767,531

TENS IONING DEVICE Fiied 001;.17. 1929 2 Sheets-Shae}. 1'

' INVENTOR. (john #67)? A TTORNE Y.

June 24,1930. J, KERR 1,767,531

' mnsIonInG DEVICE Filed Oct. 17, 1929 2 Sheets-Sheet 2 necessary in the conventional construction.

Patented June 24, 1930 10m n; Kama, or, BAY crrY, l nicn'xeii v, Assidnon ro re any. snovnts, m 1

BAY 'GITILMICHIGANK A CORPORATION OEMICHIGAN T sm memm i Application filed October 17,1929. fser' ai m, 400,362.

This invention relatesid tensioning 1 de- I vices such as used on cranes and excavating machineryin general, andmore particularly 7 to a convertible excavator which is convert- ,5 ibl e from a crane or clam shell to'a shovel attachment in which the" boom is mounted for rotation as ing movement. 7 V .i The prime object of the invention is. to

design 'a tensioning. deviceassoiciated with the bucket crowding mechanismgso that. when the bucket is loaded and the boom is raised, the device will operate andfcompen sate for the variation in distance between 2 theshaft center on the boom and'onwhich the bucket crowding mechanism is mount-v ed', andthe winding drum which is mounted .on the {excavator platform, and; which is causedby theraisi-ngfand lowering ofthef 20 boo 1 Another object is to alvrtensioning" device which will permit of a single contin 'uous chain being used, instead .ofthe double chain and the various sprockets 'and shafts A furtherobject is to provide a very :simple, substantial, and rugged devicewhich can beadjusted toasuit theltake up required,and-

which canbe very [readily manufactured and applied.

as the specification progresses, "reference be.-

reference numerals. .throu bout the several views thereof. ln fiie drawingz" f i Fig. 1 is a fragmentary-side View of. an

. ment and showingmyimproved tensioning device 1n place. V g V V Fig. 2 is a fragmentary side view of the boom in raised position.

. Fig. '3 is a fragmentary top plan View of 1 ileha nf is trained fove t e PK Qfi thence ileadin-g 7 around the sprocketii27, I 4 100 an excavating .machine.

Referring now particularly to the draw well as a raising and 'lower-' The above and othe r objectsj will excavator provided witha shovel'attach l I I .jbe hereinafter described.

excavating machine'with the device shown. in position, the dotted lines showing the i is provided] with'the usual boom fi, pivotally eonnected thereto at/the I point 7, a shaft being; journaled on the boom, at Ja interniediateits length, and .agear,9 is mounted on the fshaft, i neshing witharack 10. provided on the dipper stick, and a sprocketll is asshown; U 1 The tensioning device comprises Ta sprocket 12 mounted on a transversely disposed shaftf13which'is suitably journaled *in'brackets i l isecured ,to the faceof the. platform, said shaftglS being provided with' spaced apart opening spin which, a pair of vertically disposed, bolt 1 members .15 are also mounted on the shaft mou-nted, the lower endofieachbolt being I threaded asshown, jand nuts 1 6 and 1 7 are provided on oppositefsid'es ofgthe shaft for securing sai d-boltsin position-: Asimilar'shaftll8 is spaced fromthe shaft -,.l3cand= is "also bored in'a like manner to accommodate the bolt members,nutsl9 be ing' threaded on the bolts intermediate their length to limit the downward movementof the-shaft 18.,- similarn'uts 20- being' threaded onthe upper ends of the boltsand coiled lsprings2l are interposed between the,shaftv "1-8 :and the said nut I 20, Washers: 22 iand 23 respectively. being provided toprovide seats for [the springs, :the shafts 13. and1-18 beingjflatted so thatproper bearings are secured .for-the nutsand washers.

. T Bearings V 24;; are provided on;

in spaced apart relation, anda transversely" f v disposed shaft. 235 {is j ournaled' threiiii'links 26, connecting the shafts l8 and25,fandf a sprocket 27:is] journal-ed on magma 1 8 as chain as will shown,gandaccommodatesthe In practicea sprocket 128 'is'securedto the .windingQdrumQQ which is mounted on the shaft 30, said. shaft, being journaled: in suitable {brackets, (not shown) provided on the-excavator jplatform, and driven from the; power plant, (not shown), acontinuous 1 (thence; over the sprocket 11;, thence'backand around the sprocket 12, back to the sprocket 28, and it will be obvious that rotation of the drum driven from any suitable source of power, causes rotation of the gear for raising and lowering the bucket and crowding it into the work, and as the'boom is raised or lowered, as shown in dotted lines in Fig. 2, the sprocket 27 will be automatically shifted, and compensate for the variation in distance between the shafts 8 and 80.

Under normal operating conditions, the springs 21 are never compressed, but under extreme conditions, when the boom is lowered to the ground, the distance between centers becomes so great that the coil springs will be-compressed andpermit of a maximum downward travel of the boom.

The'position of the boom ofcourse depends on whether it is desired to dig close tothe machine, or at a point farther away intermediate the length of the boom, it is also dependentron where the excavated material is dumped, and as the boom is raised or lowered, this mechanism will compensate for the variations in the distance between the shaft centers 8 and 30, so that thechain is always tensioned, eliminating excessive strains and breakage, as well as preventing over-riding of the chain on the sprockets.

From the foregoing description it will be obvious that "I have perfected a very simple,

substantial, and effective tensioning device for excavating machinery in general.

- What I claim is I l. The combination with an excavating machine, of a tensioningldevice comprising a, transversely-disposed shaft journaled on the excavator, vertically disposed" members adjustably secured thereto, a second shaft mounted on said members, links pivotally connected thereto and to the excavator boom,

and sprockets mounted on said respective shafts. r

2; The combination with an excavating machine, of a tensioning device comprising a shaft journaledon the excavator,vertically disposed members secured thereto, a second shaft adjustably mounted on said members and spaced from the first-mentioned shaft, sprockets mounted on said shafts, and links.

connecting said second'shaft to the excavator boom.

r 3. The combination with" an excavating machine, of a tensioningdevice comprising spaced apart transversely disposed shafts,

V signature. I

posed bolts adjustably secured to said shaft, a second shaft mounted on said bolts and spaced from the first mentioned shaft, means for limiting the downward travel of said upper shaft, resilient means'interposed between said shaft and the upper ends of the bolts, and a link connecting the upper shaft to the boom of the machine.

5. The. combination with an excavating machine, ofa tensioning device comprising a transversely disposed shaft, vertically disposed bolts secured thereto, a second shaft mounted on said bolts at a point spaced from thefirst mentioned shaft, resilient means interposed between said shaft and the upper end of the bolts, sprockets journaled on said transversely disposed shafts, and links for connecting the second shaft to the excavator boom. v

6. The combination with an excavating machine, of a tensioning device comprising a transversely disposed shaft, bolts adjustably secured thereto, a second shaft mounted on said bolts and spaced from the first mentioned shaft, means for connecting said shaft to the excavator boom, sprockets on'the respective shafts,-and means interposed'between the upper shaft and the end of the bolts to permit a limited upward movement of said shaft with relation to the lower shaft.

7.111 an excavating machine provided with a boom pivotally connected thereto, a tensioning devicecomprising a-lower transversely disposed shaft, bolts secured thereto, an upper shaft spaced from the lower shaft and mounted formovement thereon, resilient means interposed between the upper shaft and the ends of the bolts, links connecting the upper shaft with-the boom, and sprock- 'ets 'journaled on the respective shafts.

8. In an excavating machine provided with a boom pivotally secured thereto, a

' tensioning'device comprising a transversely disposed lower shaft .mounted on the machine, spaced apart bolts secured'thereto, an upper shaft adjustably and slidablymounted on said bolts, resilient means interposed between said? shaft andtheupper ends of the bolts, sprockets journaled on the respective shafts, and 'links-pivotally connected to the boom and upper shaft respectively.

In testimony whereof I hereunto affix'my I JOHN M. KERR.

sprockets mounted thereon; vertically disr posed members anchored to the lower shaft,

means forsp'acing the upper shaft from the lower shaft, and resilient'means interposed between said upper members; 7

4. The combination with an excavating mashaft" and the end of the chin'eyof a tensioning device comprising a transversely disposed shaft, vertically dis- 

